Government regulations and the desire for improved fuel economy have forced motor vehicle manufacturers toward lighter weight materials. Hoods and fenders are no exception. The need for improved fuel economy has caused steel hoods to be replaced with lighter hoods comprising aluminum or fiberglass.
Fabrication of an aluminum hood requires stamping an aluminum panel using a press and a machined die. A plurality of panels may form pieces of the hood. One such hood includes left and right top sections, sides, fenders, and a grill. Manufacturers typically include additional bracing around the fender pieces to reduce fender shake and vibration. Vibration is distracting to drivers and can accelerate metal fatigue. Bracing adds to the weight of the hood.
In a metal hood, the grill often comprises steel and functions as a frame onto which the pieces are attached, directly or indirectly, using mechanical fasteners such as welds, rivets or bolts. A common bolt fastener includes a Huck® bolt. Replacement of a piece of the hood could be necessary because of damage or could be desirable for aesthetic reasons. Replacing the grill would obviously be difficult because it is the frame for the entire hood. Replacing other pieces would require removing the piece from the hood, such as with a saw and grinding tool, and attaching the new piece.
Unlike metal hoods, fiberglass hoods require no presses or dies. The absence of a press or die substantially reduces costs and time for a new design. Instead, a mold, which may be formed for example from wood or plastic, is typically used. A mold can be fabricated quickly and inexpensively. Resin-impregnated fiberglass is laid up over the mold and cured. The hood is commonly cured as a single unit, but a manufacturer could produce a plurality of pieces that are subsequently glued and laminated together. Additionally, fiberglass hoods do not rely on the grill as a structural member. The grill is easily removed or replaced. Greater aesthetic flexibility is possible with fiberglass as compared to aluminum.
Detracting from the use of fiberglass is the complexity of replacing portions of a one-piece hood. Fiberglass hoods generally lack the necessary strength to permit mechanical fastening of replacement portions. Although minor repairs can be easily made using patching compounds, repairing more substantial damage is difficult. Replacing or repairing a large portion of a fiberglass hood can be time-consuming, expensive, and likely requires professional attention. The old portion must first be removed, such as with a saw or grinding tool. The area of the hood to which the new portion is to be fixed must be sandblasted to create a clean, bondable surface. The new portion must be glued, laminated and cured to the hood. The vehicle is out of service during the duration of the repair, which could last several days.
Prior art does include a four-piece fiberglass hood comprising a center section, left and right fenders, and a metal grill. The center section includes flanges on its right and left sides. The flanges mate with a corresponding flange on the respective fender. The center flange and fender flange are secured together using a mechanical fastener, such as a rivet or bolt. Unfortunately, the flange assembly lacks mechanical strength. The unreinforced flange cannot accept a large, heavy fender, so fender options are limited. At speed, winds cause the fender to vibrate. Persistent vibration leads to mechanical fatigue and the formation of cracks in the hood assembly. Cracks ultimately lead to failure and fracture of the center section or fender.
A need exists for a hood that permits inexpensive and quick replacement of fiberglass hood pieces, particularly fenders, without the accompanying mechanical flaws of prior art. Preferably, the pieces could be of substantial weight and size, and could be modified to satisfy aesthetic preferences.